Bone and Joint Infections Flashcards
Osteomyelitis
Infection of the bone
3 mechanisms of how bone infection may be brought about
Haematogenous- bacteria in the blood seed bone
Contiguous focus-spread from adjacent area of infection
Direct incoculation-trauma or surgery
Stage 1 of osteomyelitis and likely cause
Medullary-necrosis of medullary contents- haematogenous
Stage 2 of osteomyelitis
Superficial-necrosis limited to exposed surfaces
Cause of stage 2 superficial osteomyelitis
Contiguous- Diabetic foot ulcer, pressure sores
Complications of stage 3
Necrosis- no blood supply- can’t treat with antibiotics. Surgery required to cure
Stage 3 osteomyelitis
Localised- full thickness cortical sequestation, stable before and after debridement
Stage 4 osteomyelitis
Diffuse- extensive, unstable bone
describe the pain with osteomyelitis
localised pain, not relieved with resting and progressive
Clinical presentation of osteomyelitis
Pain Soft tissue swelling Erythema Warmth Localised tenderness Reduced movement of affected limb Systemic upset uncommon (fever, chills, night sweats)
Most common causative organism of osteomyelitis (60%)
Staph A
6 main causative organisms of osteomyelitis
Staph A Stretococci Enterococci Gram -ve bacilli Anaerobes M. TB
Gold standard diagnostic procedure for osteomyelitis
Cultures and histology of bone biopsy/needle aspirate
Name 4 diagnostic tests for osteomyelitis
Gold standard
Blood cultures
Superficial swabs
C-reactive protein
When would you give empirical antimicrobial therapy in osteomyelitis?
When signs of sepsis
Which 5 antibiotics have acceptable penetrance in bone?
Clindamycin Ciprofloxacin Vancomycin Beta-Lactam Gentamicin
What is the treatment of choice for Staph A. osteomyelitis
Flucloxacillin IV
How are antibiotics usually administered in osteomyelitis?
IV
Septic arthritis
Inflammatory reaction in joint space (arthritis) caused by infection, resulting from direct invasion of the joint
2 classifications of septic arthritis
Native (natural) joint infection
Prosthetic (artificial) joint infection
2 ways in which organisms enter the joint in native joint infection
Haematogenous or trauma
How does synovial tissue facilitate ‘seeding’?
Highly vascular and lacks a basement membrane
Predisposing factors for native joint infection
RA
Trauma
IVDU
Immunosuppressive disease
Prognosis for native joint infection
Not fatal but severe lack of function if not treated
How do organisms enter the joint in prosthetic joint infections?
Haematogenous
During surgery or following wound infection after surgery
Why are prosthetic joints susceptible to infection?
Cement provides a surface for bacterial attachment
How does infection affect the joint in prosthetic infection?
Polymorph infiltration results in tissue damage instability of the prosthesis
How does infection affect the joint in native infection?
Cartilage erosion causes joint space narrowing/impaired function
Predisposing factors to prosthetic joint infection
Prior surgery at site RB Corticosteroid therapy DM Poor nutritional status Obestiy Age
Clincial presentation of septic arthritis
Pain Swelling Tenderness Redness Limitation of movement Systemic upset
Causative organisms of septic arthritis
Bacteria
Fungi e.g. candida
Viruses e.g. parovirus B19, rubella, mumps (usually self limiting part of systemic illness)
Name for group A streptococcus
Strep. pyogenes
Causative organisms for native joint infections
Staph A Streptococci A, B, C, G Gram -ve bacilli Neisseria gonorrheoae Neisseria meningitidis
Causative organisms for prosthetic joint infection
Staph A
Coagulase -ve staphylocoi
Enterococci
Gram -ve bacilli
What do you look for in an examination of joint aspirate?
High total WBCs Lots of polymorphs Gram stain- not particularly reliable Crystal examination- gout can mimic infection Culture PCR e.g. M.TB
Therapy for native joint infection
Removal of purulent material -joint drainage/washout
Empirical followed by directed antimicrobial therapy (after microbiological samples have been taken)
2-4 weeks treatment
Difference in therapy for prosthetic joint infection, compared to native
Removal of implant/replacement of some elements if unstable
2 stage revision procedure
Take out implant and replace with cement and antimicrobials before replacing
Treatment for Staph A in prosthetic joint infection
Flucoxacillin with rifampicin (Staph A. easily becomes resistant to rifampicin, so must always be used in combination for Staph A)
Duration of treatment for prosthetic joint infection
6 weeks, IV to oral switch
